Reverse individual words

Given string str, we need to print the reverse of individual words.

Examples:

Input : Hello World
Output : olleH dlroW

Input :  Geeks for Geeks
Output : skeeG rof skeeG

Method 1 (Simple): Generate all words separated by space. One by one reverse word and print them separated by space. 

Method 2 (Space Efficient): We use a stack to push all words before space. As soon as we encounter a space, we empty the stack. 

Implementation:

C++

// C++ program to reverse individual words in a given
// string using STL list

#include <bits/stdc++.h>
using namespace std;

// reverses individual words of a string
void reverseWords(string str)
{
    stack<char> st;

    // Traverse given string and push all characters
    // to stack until we see a space.
    for (int i = 0; i < str.length(); ++i) {
        if (str[i] != ' ')
            st.push(str[i]);

        // When we see a space, we print contents
        // of stack.
        else {
            while (st.empty() == false) {
                cout << st.top();
                st.pop();
            }
            cout << " ";
        }
    }

    // Since there may not be space after
    // last word.
    while (st.empty() == false) {
        cout << st.top();
        st.pop();
    }
}

// Driver program to test function
int main()
{
    string str = "Geeks for Geeks";
    reverseWords(str);
    return 0;
}

C#

// C# program to reverse individual
// words in a given string using STL list
using System;
using System.Collections.Generic;

class GFG
{

// reverses individual words
// of a string
public static void reverseWords(string str)
{
    Stack<char> st = new Stack<char>();

    // Traverse given string and push
    // all characters to stack until
    // we see a space.
    for (int i = 0; i < str.Length; ++i)
    {
        if (str[i] != ' ')
        {
            st.Push(str[i]);
        }

        // When we see a space, we
        // print contents of stack.
        else
        {
            while (st.Count > 0)
            {
                Console.Write(st.Pop());

            }
            Console.Write(" ");
        }
    }

    // Since there may not be
    // space after last word.
    while (st.Count > 0)
    {
        Console.Write(st.Pop());

    }
}

// Driver Code
public static void Main(string[] args)
{
    string str = "Geeks for Geeks";
    reverseWords(str);
}
}

// This code is contributed
// by Shrikant13

Java

// Java program to reverse individual
// words in a given string using STL list
import java.io.*;
import java.util.*;

class GFG {

    // reverses individual words of a string
    static void reverseWords(String str)
    {
        Stack<Character> st = new Stack<Character>();

        // Traverse given string and push all
        // characters to stack until we see a space.
        for (int i = 0; i < str.length(); ++i) {
            if (str.charAt(i) != ' ')
                st.push(str.charAt(i));

            // When we see a space, we print
            // contents of stack.
            else {
                while (st.empty() == false) {
                    System.out.print(st.pop());
                }
                System.out.print(" ");
            }
        }

        // Since there may not be space after
        // last word.
        while (st.empty() == false) {
            System.out.print(st.pop());
        }
    }

    // Driver program to test above function
    public static void main(String[] args)
    {
        String str = "Geeks for Geeks";
        reverseWords(str);
    }
}

Python3

# Python3 program to reverse individual words
# in a given string using STL list

# reverses individual words of a string


def reverseWords(string):
    st = list()

    # Traverse given string and push all characters
    # to stack until we see a space.
    for i in range(len(string)):
        if string[i] != " ":
            st.append(string[i])

        # When we see a space, we print
        # contents of stack.
        else:
            while len(st) > 0:
                print(st[-1], end="")
                st.pop()
            print(end=" ")

    # Since there may not be space after
    # last word.
    while len(st) > 0:
        print(st[-1], end="")
        st.pop()


# Driver Code
if __name__ == "__main__":
    string = "Geeks for Geeks"
    reverseWords(string)

# This code is contributed by
# sanjeev2552

Javascript

// JS program to reverse individual words in a given
// string using STL list


// reverses individual words of a string
function reverseWords(str) {
    let st = [];

    // Traverse given string and push all characters
    // to stack until we see a space.
    for (let i = 0; i < str.length; ++i) {
        if (str[i] != ' ')
            st.unshift(str[i]);

        // When we see a space, we print contents
        // of stack.
        else {
            while (st.length != 0) {
                console.log(st[0]);
               st.shift();
            }
        }
    }

    // Since there may not be space after
    // last word.
    while (st.length != 0) {
        console.log(st[0]);
        st.shift();
    }
}

// Driver program to test function
let str = "Geeks for Geeks";
reverseWords(str);

// This code is contributed by adityamaharshi21

Output

skeeG rof skeeG

Time Complexity: O(n), where n is the length of the string
Auxiliary Space: O(n), where n is the length of the string

Python | Reverse each word in a sentence

Using stringstream in C++ : 

Implementation:

C#

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text;
using System.IO;

public class GFG {
    static void printWords(string str)
    {
        // word variable to store word
        string word;

        // making a string stream
        using(var iss = new StringReader(str))
        {
            string line;
            while ((line = iss.ReadLine()) != null) {
                // Read and print each word.
                foreach(string w in line.Split(' '))
                {
                    word
                        = new string(w.Reverse().ToArray());
                    Console.Write(word + " ");
                }
            }
        }
    }

    // Driver code
    static void Main()
    {
        string s = "GeeksforGeeks is good to learn";
        printWords(s);
    }
}
// ksam24000

CPP

#include <bits/stdc++.h>
using namespace std;

void printWords(string str)
{
    // word variable to store word
    string word;

    // making a string stream
    stringstream iss(str);

    // Read and print each word.
    while (iss >> word) {
        reverse(word.begin(), word.end());
        cout << word << " ";
    }
}

// Driver code
int main()
{
    string s = "GeeksforGeeks is good to learn";
    printWords(s);
    return 0;
}
// This code is contributed by Nikhil Rawat

Java

import java.io.*;
import java.lang.*;
import java.util.*;

class Main {
    public static void printWords(String str)
    {
        // word variable to store word
        String word;

        // making a string stream
        StringTokenizer iss = new StringTokenizer(str);

        // Read and print each word.
        while (iss.hasMoreTokens()) {
            word = iss.nextToken();
            System.out.print(
                new StringBuilder(word).reverse().toString()
                + " ");
        }
    }

    public static void main(String[] args)
        throws java.lang.Exception
    {
        String s = "GeeksforGeeks is good to learn";
        printWords(s);
    }
}

// Contributed by rishabmalhdijo

Python3

def print_words(s):
    # word variable to store word
    word = ""

    # making a string stream
    iss = s.split()

    # Read and print each word.
    for i in iss:
        word = i[::-1]
        print(word, end=" ")


# Driver code
if __name__ == '__main__':
    s = "GeeksforGeeks is good to learn"
    print_words(s)

Output

skeeGrofskeeG si doog ot nrael 

Time complexity : O(n) 
Auxiliary Space : O(n)

Using Java 8 Streams:

Implementation:

Java

import java.util.Arrays;
import java.util.stream.Collectors;

// This code is contributed by Mayank Sharma
public class reverseIndividual {

    public static void main(String[] args) {

        String str = "Welcome to GFG";

        // Splitting the string based on space and reverse each part
        // and then join
        String result = Arrays.asList(str.split(" "))
                .stream()
                .map(s -> new StringBuilder(s).reverse())
                .collect(Collectors.joining(" "));

        System.out.println(result);

    }

}

Python3

# python code

import re

def reverseIndividual(str):
    words = re.findall(r'\b\w+\b', str)
    result = " ".join(word[::-1] for word in words)
    return result

str = "Welcome to GFG"
print(reverseIndividual(str))

#code by ksam24000

C++

#include <bits/stdc++.h>
using namespace std;

int main() {
string str = "Welcome to GFG";
    string result = "";

    // Splitting the string based on space
    istringstream ss(str);
    vector<string> words;
    do {
        string word;
        ss >> word;
        words.push_back(word);
    } while (ss);

    // Reverse each part and then join
    for (int i = 0; i < words.size() - 1; i++) {
        reverse(words[i].begin(), words[i].end());
        result += words[i] + ' ';
    }
    reverse(words.back().begin(), words.back().end());
    result += words.back();

    cout << result << endl;
    return 0;
}
//This code is contributed by Shivam Tiwari

C#

using System;
using System.Linq;

public class ReverseIndividual
{
    public static void Main(string[] args)
    {
        string str = "Welcome to GFG";

        // Splitting the string based on space and reverse each part
        // and then join
        string result = string.Join(" ", str.Split(' ')
            .Select(word => new string(word.Reverse().ToArray())));

        Console.WriteLine(result);
    }
}

Output

emocleW ot GFG

Time complexity : O(n) 
Auxiliary Space: O(n)

Way 3: Using StringBuffer Class.

Approach:

1. O(n) First, convert the string object into a StringBuffer object.
2. By using the reverse method of the StringBuffer class reverse the string.
3. Now, store the reverse sequence in a String array.
4. Run a loop that will create a new String by using these reverse words
5. Finally, return the new string.

Implementation:

C++

#include <algorithm>
#include <iostream>
#include <sstream>
#include <string>

std::string makeReverse(std::string str)
{
    std::reverse(str.begin(), str.end());
    std::istringstream iss(str);
    std::string word;
    std::string reverse;
    while (iss >> word) {
        reverse = word + " " + reverse;
    }
    return reverse;
}

int main()
{
    std::string str = "Geeks for Geeks";
    std::cout << makeReverse(str) << std::endl;
    return 0;
}

Java

/*package whatever //do not write package name here */

import java.io.*;

class GFG {
    static String makeReverse(String str)
    {
        StringBuffer s = new StringBuffer(str);
        str = s.reverse().toString();
        String[] rev = str.split(" ");
        StringBuffer reverse = new StringBuffer();
        for (int i = rev.length - 1; i >= 0; i--) {
            reverse.append(rev[i]).append(" ");
        }
        return reverse.toString();
    }
    public static void main(String[] args)
    {
        String str = "Geeks for Geeks";
        System.out.println(makeReverse(str));
    }
}

// This code is contributed by Adarsh Kumar

Python3

# Function to make the reverse of the string
def make_reverse(string: str) -> str:
    # Reversing the string
    string = string[::-1]
    # Splitting the string by space
    rev = string.split(" ")
    # Reversing the list of words
    rev = rev[::-1]
    # Joining the words to form a new string
    reversed_string = " ".join(rev)
    return reversed_string


# Driver code
if __name__ == "__main__":
    string = "Geeks for Geeks"
    print(make_reverse(string))

# This code is contributed by Shivam Tiwari

Output

skeeG rof skeeG 

Time complexity : O(n) 
Auxiliary Space : O(n)

Way 4:

Approach: To store the reversed string instead of just printing

Steps:

1. Create a stack and push all the characters of the given input string.
2. Create  ‘rev’ and ‘temp’ strings
3. Do the following steps till the stack becomes empty.
4. If the peek( ) of the stack is a character, append it to temp.
5. If the peek( ) of the stack is a space, then append space to rev and also temp to rev
6. Finally, if the temp is not empty, append the temp to rev in the front
7. Return the reversed string.

Implementation:

Java

// Java program to reverse the individual words

import java.util.Stack;

public class Reverse {

    // function to reverse the individual words
    String reverse(String str)
    {
        // create a stack to access the string from end
        Stack<Character> s = new Stack<>();

        // push all the characters of the stack
        for (int i = 0; i < str.length(); i++)
            s.push(str.charAt(i));

        // rev string to store the required output
        String rev = "";
        String temp = "";

        // till the stack becomes empty
        while (!s.isEmpty()) {
            // if top of the stack is a letter,
            // then append it to temp;
            if (Character.isLetter(s.peek()))
                temp = temp + s.pop();
            // if it is a space, the append space to rev
            // and also temp to rev
            else {
                rev = " " + temp + rev;
                // make the temp empty
                temp = "";
                s.pop();
            }
        }
        // if temp is not empty, add temp to rev at the
        // front
        if (temp != "")
            rev = temp + rev;

        // return the output string
        return rev;
    }

    public static void main(String[] args)
    {
        String str = "Geeks for Geeks";

        Reverse obj = new Reverse();
        System.out.println(obj.reverse(str));
    }
}

// This method is contributed by Likhita AVL

Output

skeeG rof skeeG

Time Complexity: O(n)
Auxiliary Space:: O(n) 
for using stack.

Using Split and iterator in Python

Implementation:

Python3

def rev_sentence(sentence):

    # first split the string into words
    words = sentence.split(' ')
    reverse_sentence = ""
    for i in words:
        reverse_sentence += i[::-1]+' '
    # then reverse the split string list and join using space

    # finally return the joined string
    return reverse_sentence


if __name__ == "__main__":
    input = 'geeks quiz practice code'
    print(rev_sentence(input))

Output

skeeg ziuq ecitcarp edoc 

Time Complexity: O(n)
Auxiliary Space:: O(n)

Method: Using join and split functions

Implementation:

Python3

# Python code to reverse words

s = " Geeks for Geeks"
l = []
# splitting the string
s = s.split()
for i in s:
    # reversing each word
    l.append(i[::-1])
# printing string using join

# function after reversing the
# words


print(" ".join(l))

Output

skeeG rof skeeG

Time Complexity: O(n) 
Auxiliary Space: O(n)